opencv template matching

#include<stdio.h>
#include"cv.h"
#include"highgui.h"

int main(int argc,char** argv)
{
  IplImage  *img;
  IplImage  *tpl;
  IplImage  *res;
  CvPoint   minloc, maxloc;
  double    minval, maxval;

  /* check for arguments */
  if(argc <3){
    fprintf(stderr,"Usage: template_match <reference> <template>\n");
    return1;
  }

  /* load reference image */
  img = cvLoadImage(argv[1], CV_LOAD_IMAGE_COLOR);

  /* always check */
  if(img ==0){
    printf("Cannot load file %s!\n", argv[1]);
    return1;
  }

  /* load template image */
  tpl = cvLoadImage(argv[2], CV_LOAD_IMAGE_COLOR);

  /* always check */
  if(tpl ==0){
    printf("Cannot load file %s!\n", argv[2]);
    return1;
  }

  CvSize size = cvSize(
    img->width  - tpl->width  +1,
    img->height - tpl->height +1
  );

  /* create new image for template matching computation */
  res = cvCreateImage(size, IPL_DEPTH_32F,1);

  /* choose template matching method to be used */
  cvMatchTemplate(img, tpl, res, CV_TM_SQDIFF);
  /*cvMatchTemplate(img, tpl, res, CV_TM_SQDIFF_NORMED);
  cvMatchTemplate(img, tpl, res, CV_TM_CCORR);
  cvMatchTemplate(img, tpl, res, CV_TM_CCORR_NORMED);
  cvMatchTemplate(img, tpl, res, CV_TM_CCOEFF);
  cvMatchTemplate(img, tpl, res, CV_TM_CCOEFF_NORMED);*/

  cvMinMaxLoc(res,&minval,&maxval,&minloc,&maxloc,0);

  /* draw red rectangle */
  cvRectangle(img,
         cvPoint(minloc.x, minloc.y),
         cvPoint(minloc.x + tpl->width, minloc.y + tpl->height),
         CV_RGB(255,0,0),1,0,0);  

  /* display images */
  cvNamedWindow("reference", CV_WINDOW_AUTOSIZE);
  cvNamedWindow("template", CV_WINDOW_AUTOSIZE);
  cvShowImage("reference", img);
  cvShowImage("template", tpl);

  /* wait until user press a key to exit */
  cvWaitKey(0);

  /* free memory */
  cvDestroyWindow("reference");
  cvDestroyWindow("template");
  cvReleaseImage(&img);
  cvReleaseImage(&tpl);
  cvReleaseImage(&res);

  return0;
}